Cells exhibit rich repertoire of dynamical behaviors, which depend on cell phenotype and microenvironment. The collective dynamics of cells has gathered increasing attention inspiring experimental and theoretical studies in an attempt to unravel the underlying physical principles. Using in vitro experiments, we show that very different cell types self-organize in a bi-dimensional nematic phase with characteristic ±1/2 nematic defects. I will present examples of (1) spontaneous symmetry breaking and the emergence of shear flows of spindle-shaped cells when confined in adhesive stripes; (2) existence of nematic turbulent phase driven by cell activity in epithelial cell monolayers; and (3) conditions for the appearance of activity driven turbulence in a confined environment. I will discuss physical mechanisms of these out of equilibrium phenomena and their effect on tissue organization and biological function.